1. Field of the Invention
The present invention relates to an electrostatic chuck for use in manufacturing a semiconductor device and the like.
2. Description of the Related Art
Heretofore, in processing steps such as exposure, physical vapor deposition (PVD), chemical vapor deposition (CVD) and etching in manufacture of a semiconductor device and a liquid crystal device, an electrostatic chuck which attracts and holds a semiconductor substrate and a glass substrate has been used (for example, refer to Japanese Patent Laid-Open Publication No. 2002-93894).
The electrostatic chuck is constructed by bonding, for example, a base made of ceramics and a cooling member made of aluminum to each other by using an organic bonding material such as silicone resin and acrylic resin. When the organic bonding material is heated up to a temperature of 100° C. or more, bonding force thereof is reduced to a large extent.
Here, the ceramics and the aluminum are different from each other in thermal expansion coefficient, and accordingly, when the electrostatic chuck is heated up, stresses occur on a bonded interface between the base and the boding material, and on a bonded interface between the cooling member and the bonding material.
Meanwhile, a processing temperature in the etching and the like has heretofore been 100° C. or less as a mainstream; however, the processing temperature has reached 100 to 200° C. recently, and development of an electrostatic chuck usable in such a temperature range has been implemented.
However, the conventional electrostatic chuck described above is constructed by the bonding using the organic bonding material, and accordingly, when the electrostatic chuck is used at a temperature as high as 100° C. or more, there has been a possibility that exfoliation occurs in such a bonded portion of the base and the cooling member (specifically, the bonded interface between the base and the bonding material, and the bonded interface between the bonding material and the cooling member), and that gas tightness in the bonded interfaces described above is thus reduced. As a result, there has been a possibility that gas to be provided onto a substrate mounting surface of a surface of the base through a gas providing passage passes through the above-described bonded interfaces, and leaks to an outside of the electrostatic chuck (that is, into a chamber).
Note that a method is also conceivable, which performs the bonding by using a sheet of metal such as aluminum in place of the organic bonding material. However, in this case, it has been necessary to fabricate the cooling member by a material (for example, an Al—SiC composite material) whose thermal expansion coefficient is adjusted very approximately to the thermal expansion coefficient of the ceramics, causing a problem that cost is increased to an extremely large extent.